..two centuries worth of observation indicate a disproportionate amount of comets originate from the outer regions of the Oort Cloud as opposed to the areas closer to the Sun. A planet anywhere from one to four times the mass of Jupiter could be responsible for the gravitational influence that would create this imbalance. Matese points out that the probability that this effect is purely a statistical fluke is extremely small, which suggests there’s something strange going on out there in the outer Oort. Tyche might also be responsible for the unusually elongated orbit of the dwarf planet Sedna.
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If the planet exists, it would be located some 30,000 astronomical units away, meaning its distance from the Sun is 30,000 times that of Earth. It be extremely cold, with a temperature of about -73 degrees Celsius. At such a freezing temperature, Tyche would radiate no heat for us to detect, and its extreme distance would make it incredibly hard to spot. By comparison, Neptune is only 30 astronomical units away, and the Kuiper Belt is just 55 AU from the Sun. (via Gigantic hidden planet could be hurling comets at the rest of the solar system)
The Committee to Nuke Elysium 